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Mandar Gokhale's weblog on the internets

DNS Trivia: Country Codes and the .gb Domain

This week, we were discussing ccTLD (country code Top Level Domain) confusion at work – specifically in the context of the .om toplevel domain, which apparently is used for tricking people into visiting foo.co.om instead of foo.com.

This led me to dig a little more into how exactly the ccTLDs for each country are assigned. RFC 1591 tells us that they are taken straight from ISO-3166. However, as always, there are exceptions. There are a handful of unused ones from small, obscure regions round the world (including, amusingly, .um and .eh) – but there is one rather large exception. The ISO-3166 country code for the United Kingdom is GB, but the domain used by them is the well-known .uk.

You’d think the story ends there, but it doesn’t. Apparently .gb was created and used at some point, and so it is still available from DNS root (although not open for registration). I think this technically makes the UK the only country to have two ccTLDs. And there is a dwindling number of servers out there that still answer serve DNS records over the .gb domain.

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{~}$ dig +noall +answer A delos.dra.hmg.gb
delos.dra.hmg.gb. 86400   IN  A   146.80.9.105

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